Defibrillators and defibrillator-external pacemakers are employed to restore and maintain a heart's normal rhythm in either an emergency situation such as cardiac arrest, or voluntarily to normalize a person's rhythm in non-life threatening situations (e.g., atrial fibrillation).
Use of a defibrillator requires specific certification resulting from such programs as the American Heart Association's Advanced Life or Base Life Support courses. Further institutional or organizational training or competency evaluation may also be required. These requirements generally remain true for both manual and semi-automatic (AED) defibrillators. In order to maximize familiarity with this lifesaving equipment, institutions and organizations generally require periodic recertification and or demonstration of competency. In part, these training requirements are an attempt to maximize an operator's chance of successfully using a defibrillator.
Use of a defibrillator, particularly in emergency situations, places a great deal of stress on its operator. As such, even trained users still make mistakes when trying to operate a defibrillator. At least one study has demonstrated that upwards of 50 percent of defibrillator failures can be attributed to operator errors. Failure to use the defibrillator correctly can cause delays and compromise therapy. Bone, Defibrillator Failures: Causes and Problems and Recommendations for Improvement, JAMA, Vol. 264, No. 8 (1990).
Another factor contributing to operator errors is that many institutions and organizations possess different models of defibrillators that employ different operating interfaces, terminology, etc. The difference in operating systems can cause delays and mistakes, both of which may compromise therapy.
Operators are generally required to perform daily test and maintenance on a defibrillator. Such activities may require operation from a DC (battery) source that leads one to disconnect the defibrillator from AC power source. It is not beyond reason that an operator, after completing a daily test might leave the defibrillator in the powered on condition, and not connect to the AC power source. Such conditions would drain the battery and render the defibrillator therapeutically useless. Another such example might be the disconnecting of therapeutic electrodes for daily test purposes. If not reconnected, delays might result that compromise therapy.
The current state of the art employs visual prompts or nonspecific tones to communicate user errors, and/or communicate corrective actions to defibrillator operators. FIG. 6 gives an example of a prior art visual prompt for communicating a user error. A recognized shortcoming of visual prompts is that they can be easily overlooked under the stress of an emergency situation. They are passive as this approach relies on an operator looking specifically at the display field at all times. Newer AED defibrillators have taken the step of incorporating graphic prompts or icons into the physical design and labeling of the product in order to give them more permanency.
In an attempt to overcome these shortcomings, some defibrillators have incorporated a variety of high and low pitched tones as alert alarms to draw attention to the device. Initially successful, their shortcoming has become a lack of specificity. Over the years there has been proliferation of tonal alarms on a variety of medical equipment likely to be present in an emergency resuscitation. Further, the growing trend toward incorporating more vital sign parameters into pre-hospital defibrillators also raises the number of warning tones rescuers must decipher.
In recent years voice prompts have been employed to simplify the therapeutic use of defibrillators. That is they guide users, some minimally trained, through the setup and use of a defibrillator for delivery of a potentially lifesaving electrical shock (e.g., attaching electrodes, prompting need for CPR, and shock delivery). Most recently, defibrillators have begun to expand the range of the voice prompting to include the ABCs (airway, breathing, chest compressions) of resuscitation, and to provide feedback on the quality and rate of chest compressions. Olson U.S. Pat. No. 5,792,190 and Edward U.S. Application No. 2003/0216785 describe the use of voice prompts as part of an AED interface; they generally describe the role of voice prompts as instructions for a series of operations performed by the operator for the treatment of a patient, including the deployment and use of an AED. Nova U.S. Pat. Nos. 6,334,070 and 6,697,671 and Snyder U.S. Pat. No. 6,356,785 expand the use of therapeutic voice prompts to include BLS and ALS treatment protocols; operational faults are communicated to the operator by visual indicators (e.g., LED) or non-specific tonal sounds. Stendahl U.S. Pat. No. 5,955,956 describes the use of an audible alarm system in an AED in response to processor detected faults that are found during a periodic self-test. Borgenicht U.S. Pat. No. 6,405,082 describes the use of tonal and verbal prompts to confirm the therapeutic modes of a defibrillator, i.e., to alert the operator that the defibrillation mode has been selected, or that one is charging for synchronized cardioversion.